1. Field of the Invention A method of degrading biodegradable waste through bioaugmentation by transporting the biodegradable waste through a multistage apparatus.
2. Description of the Prior Art
Sewage from residental, commercial and business sources are commonly processed at a central treatment plant where sewage is treated to allow the resulting product to returned to the ecological system. However, if uncontrolled, certain types of sewage high in organic matter such as grease may clog such collection systems. Moreover, pumping stations are frequently used to transport the sewage to the treatment plant. These locations collect grease and other organic matter not decomposed within the water flow. Thus, it is necessary to clean the pumping stations or other junction points in the system where grease and other organic matter collect.
Bacterial augmentation to induce organic degrading has been introduced to reduce or eliminate the need for continuous removal thereof. A bacterial supplement of highly-cultured strains of bacteria for specific organic reduction are employed. These bacterial strains are selected to reduce and convert the grease and other organic matter to lower molecular weight compounds which will not accumulate within the sewage systems.
The anaerobic digestion of materials is discussed by John F. Andrews in "Control Strategies for the Anaerobic Digestion Process, Part I" in Water and Sewage Works, March, 1975. Anaerobic digestion is described as occuring in two steps; the acid fermentation stage and the methane fermentation stage.
In the second stage, highly obligate anaerobes, collectively known as methane formers, are required. The presence of any free or dissolved oxygen will destroy or at least severely inhibit further digestion because of the oxygen-sensitivity of the methane formers. A true anaerobic system must not contain any available or free oxygen.
Andrews reveals that the acid-producing bacteria are less susceptible than the methane bacteria to changes in environmental conditions such as pH, temperature and inhibitory substances. Moreover, because most species of methane bacteria have much lower growth rates than the acid producing bacteria, the rate-limiting step in the overall anaerobic digestion process is the conversion by the methane bacteria of the intermediate products.
Recognizing the methane fermentation stage to be the rate limiting step of the anaerobic digestion process, suggestions have been advanced in the art to accelerate the reaction rates of that step. For example, a two-phase anaerobic digestion process may be used in which the acid and methane formers are provided with optimum environments in separate acid and methane fermentation reactors connected in series.
U.S. Pat. No. 4,094,773 discloses an anaerobic process comprising three steps having progressively higher temperatures for digesting raw household sewage with methane forming bacteria. After a sterilization fourth stage the effluent is treated in a ground filter. Heat is countercurrently transferred from the sterilization stage effluent to the substrate of the digestion stages. The apparatus for carrying out this process has an underlying heat-exchange compartment and four concentric compartments, of which the innermost is the sterilization stage compartment containing a heating means and the outermost compartments are flow chambers for sequentially digesting the sewage prior to sterilizing. Sterilized effluent from the fourth stage passes through the underlying heat-exchange compartment to the bottom of the three concentric flow chambers.
U.S. Pat. No. 4,670,149 shows a bacterial incubator device to facilitate organic reduction of waste materials through the addition of culture strains of bacteria with a high capacity for specific organic reduction. The bacterial incubator device includes an enclosure having a foraminous wall structure packed with high surface area elements to increase the solid bacterial growth surface area.
Additional examples of the prior art are found in U.S. Pat. Nos. 3,957,634; 4,077,877 and 4,587,019.